Correcting device for the control of gearboxes



L. PERAS March 22, 1960 CORRECTING DEVICE FOR THE CONTROL OF GEARBOXES Filed Nov. 22, 1955 2 Sheets-Sheet J.

March 22, 1960 PERAS 2,929,256

CORRECTING DEVICE FOR THE CONTROL OF GEARBOXES Filed Nov. 22, 1955 2 Sheets-Sheet 2 CORRECTING DEVICE FDR THE CONTROL F GEAOXES Lucien Pei-as, Billanconrt, France, assignor to Regie Na- The invention relates to automatically controlled gearboxes, and concerns a correcting device for the control of the boxes. The corrector which forms the subject of the invention is applicable to devices for automatic control of gearboxes wherein a change from one speed ratio to the next higher ratio is controlled by an electrical relay whereof the coil is fed by a variable current, in accordance with a predetermined law, as a function of the speed of a shaft in the transmission, and if desired as a function of the torque transmitted by the engine or of a magnitude bound up with this torque.

Several automatic control devices for gearboxes be,- longing to this category are known:

In some, the current feeding the relay coil is provided by a DC, A.C. or rectified A.C. generator driven by the shaft the rotational speed of which is intended to participate in the control.

In another system the relay coil is fed by current impulses whereof the mean intensity is proportional to the number of contacts set up, during a fixed time, interval, bye contact breaker connected to the shaft, the rotational speed of which is intended to participate in the control.

In all the devices mentioned above, the main relay is so regulated as to cause a change from one speed stage of the box to the next higher speed stage at a value I of the mean current flowing through the coil, and to cause a return from the higher ratio to the lower ratio at a mean intensity i lower than the intensity I previously mentioned.

The intensities I and i correspond, at maximum engine torque, to vehicle speeds V and v.

In order to avoid hunting phenomena, that is to say successive and untimely changes from the lower ratio to the higher ratio and vice versa, it is necessary for the speeds V and v to be distinctly different from one another.

It is advantageous so to choose V that it represents the optimum point for a change from the lower ratio to the higher ratio, that is to say that a higher force is obtained at the road wheels in the lower ratio for all values of vehicle speed lower than V, and a higher force is obtained at the road wheels for all values greater than V in the higher ratio.

When the gear box is in the higher ratio, it is impossible to re-engage the lower ratio, which would give a higher force at the road wheels, at any speed between v and V, since, by construction, this operation is only possible by disengagement of the relay if the speed falls below the value v.

A known method of overcoming this disadvantage is the use of devices in which a particular operation, consisting for example in pressing the accelerator pedal of the vehicle beyond the position corresponding to'norma'l running at full throttle, acts on a switch which cuts out the action of the relay and forcibly causes a change from the higher ratio to the lower ratio, no matter what the speed of the vehicle.

These systems have the disadvantage of leaving it to the driver to determine the speed at which it is appro- 2,929,25fi Patented Mar. 22, 1960 priate to allow the automatic gearbox to change back to the higher ratio by ceasing to operate the device in question. If the driver selects this speed above or below the optimum speed V, which he cannot determine as precisely as the maker of the vehicle, he will not have the benefit of optimum force at the road wheels, and, which is more serious, he can be tempted only to change into the higher ratio at a speed greatly in excess of V, or even to make the automatic gearbox change back from the higher ratio to the lower ratio at such a speed, which involves the risk of making the engine work at speeds which may be harmful to it.

The object of the invention is to allow the driver to cause a change into that one of the ratios corresponding to the disengaged position of the relay by an operation consisting, for example, of pressing once, and for a time which may be very short, on the accelerator pedal beyond the position corresponding to full throttle, and only when the intensity flowing through the relay coil is between the engagement and disengagement values, by acting on a time delay switch or a change-over switch under certain conditions as set out below:

In the attached drawing:

Fig. 1 and 2 represent two variants of an embodimen only causing opening or closing of circuits by time delay switches;

Figs. 3 and 4 represent two other variants wherein only simple change-over switches and condensers are used in accordance with a preferred form of the invention.

In all these figures, 1 represents a variable current source, for generating pulsating current; whose meanin= tensity of the impulses generated is proportional tothe number of contacts made by the contacts of a contactor or make-and-break means 190perated by a cam driven by a shaft 20, the rotational speed of which controls the impulses from a source of indirectional current 21. This current varies as a function of the speed of the shaft 20in the transmission, and possibly of the load on the en'-' gine 22. The variable current source is connected by the conductors 2 and 3 to the relay coil, 4; The armature 5 of this relay, carries a contact 6, which, when the current intensity circulating in the coil reaches the value I, touches the contact 7 and closes thev circuit, 8, which causes a variable gearbox 23 to change into a higher ratio by means outside the scope of the present invention.

The contacts 6; and 7 of the relay separate when the intensity flowing through the coil falls below the value i. Interruption of the current in the circuit 8, causes, a change from; a higher ratio to the lower ratio. A change-over switch 9 or a time delay switch A, has a contact 10 operable from its position shown in Fig. 3 bridging one of a pair of contacts with contact 13} ton position in which it bridges contact 14 and the other contact of said pair when an accelerator pedal 24 is depressed beyond its position 25 which corresponds to a full throttle position.

In the case of Fig. 1, a time delay switchof known type, a description of which isoutside the scope of the invention, and cutting off the current. for a predetermined time when it is operated, is connected int'series' at A- in the circuit formed by the source I'and the coil'4'.

In the case of Fig. 2, a time delay switch, likewise ofknown type, setting up contact fora predetermined time when it is operated, is connected in parallel with the relay coil 2 at B.

In the caseof'Fig. 3, the change-over switch "9 whereof the moving member 10, electrically connected to one plate 11 of a condenser of which the other plate 12 is connected to one of the conductors 3 feeding the relay coil, andnormally to its rest contact 13 likewise connected to the conductor 3, allows the .plate- 11 ofthe condenser to,

be connected to the conductor 2 when operated and the moving member touches the contact 14.

In the case of Fig. 4, the. core of the relay carries an auxiliary demagnetising coil in addition to the main coil 4. 4 As in the preceding case, the moving member 10 of a change-over switch 9 has a rest contact 13 and a working contact 14. When the moving member is on the. contact 13, it sets up contact between one plate 11 of a condenser and one of the poles 16 of a voltage source 17, the other plate of the condenser being permanently connected to the other pole 18 of the source 17. When themoving member 10 touches the contact 14, it connects the plate 11 to one end of the coil 15, of which the other end is connected to-the conductor 18. 1 In.a particular case, the source 17 can be merged with the source 1. I g I Y In another particular case, the coil 15 can be placed on a core distinct from that of the coil'4, and act directly onfthe armature 5, or on a member connected to the latter.

The appliance operates as follows:

In-the fourexamples of embodiment previously described, a single operation of the switch or change-over switch effected by the driver, either manually or preferably by pressing the accelerator pedal 24 beyond the fully open position 25, causes a short interruption of the attracting force of the coil 4 on the armature 5 of the "relay. V

* 'In the case of Fig.- 1, the current flowing through the coil 4 is purely and simply cut off during the period of operation of the' switch.

In the case of Fig. 2, the coil 4 is short-circuited during the period of operation of the switch, and is traversed only by a current of negligible intensity while contact is set up by the switch.

In the case of Fig. 3, placing the condenser 11-42 in parallel with the coil 4 sets up a current shunt during the charging time of the condenser, which momentarily decreases the current flowing through the coil 4.

In the case of Fig. 4, the condenser 1112, which in the-rest position is charged up to the voltage of the source 17, discharges, when the change-over switch is operated, into the demagnetising winding 15, which momentarily decreases the attraction'of the relay on the armature 5.

The period of decrease of'attraction on the armature of the relay 'must in all cases be made large enough to causethe relay to disengage, and short enough so that, if the switch or the change-over switch is operated when the current flowing through the coil is of an intensity.

greater than I, the period of interruption of current in the circuit 8 hasyirtualIy no influence on the operation of the automatic gearbox 23, which should remain in the higher ratio.

- The effect of operating the switch or the change-over switch on thedriving of the vehicle varies in accordance with its speed. a

Three cases may be distinguished:

If the speed of the vehicle is at this moment lower than -v, the relay is in the disengaged position, and the gearbox in the lower ratio. The decrease of the magnetic field in the core of the relay consequently'cannot alter the position of "the armature 5, which remains in any case disengaged, and operation of the switch of the change- .over switch has no effect on the running of the vehicle.

If the speed of the vehicle is between v and V, and the relay has not been previously engaged, the gearbox is consequently in the lower ratio, and everything happens asin the preceding case. t

If the speed of the vehicle is between v and V, the relay having been previously engaged and the gearbox being consequently in the higher ratio, operation by the driver of the switch or change-over switch de-energises the, relay for a time sufficient to cause it to disengage. The gearbox then changes into the lower ratio. When inter up on; cit-the ener-s qs cease e c nt flo in the coil 4 resumes its former value between i and I. It is consequently insufiicient to cause re-engagement of the relay, and the gearboxremains in the lower ratio. It is this operation which justifies the use of the device according to the invention, and allows the driver to select the lower ratio at will when this ratio is advantageous for obtaining maximum effect at the road Wheels, that is to say at a vehicle speed less than V.

If the vehicle speed is greater than V, interruption of the energising will disengage the relay, but the latter will re-engage immediately, since its coil 4 will again be traversed by an intensity of a value greater than I. In view of the fact that by construction, as indicated above, the period of interruption is short enough not to allow time for a change in gearbox ratio to take place, operation of the switch will have no action, and consequently will not be disadvantageous as regards the running of the vehicle. It will he understood that what has been said regarding the example arrangement concerning an overdrive for changing between two ratios is equally applicable to an arrangement in which a change is effected between two successive gear ratios of a variable gearbox having more than two gear ratios.

I claim:

1. In a vehicle having an automatic variable gearbox shiftable. between lower and higher gear ratios, an electrical control device for operably controlling and operating the automatic gearbox between said lower and higher gear ratios comprising, an electrical control circuit having a current source generating variable current values in dependence upon the speed of the vehicle, an energizing branch circuit connected to receive current fromsaid source, an actuating branch circuit connected to control actuation of said automatic gearbox, currentresponsive means .operatively connected in said energizing circuit for opening and closing said actuating branch circuit in dependence upon predetermined values of current flowing in said energizing circuit, said gearbox having means to shift to a higher gear ratio when said current-responsive means is actuated in a forward position closing said actuating branch circuit and to shift to a lower gear ratio when the current-responsive meansvis actuated to a resulting position opening said actuating branch circuit, the current-responsive means having means for automatically actuating it to a forward position from a resetting position at a first current value corresponding to a first speed of the vehicle and for automatically actuating it to a resetting position at a lower second current value corresponding to a second speed of the vehicle lower than the first mentioned speed, means comprising a changeover switch operable at will connected in the energizing circuit for causing the current responsive means to be actuated to the resetting position at a predetermined third current value lower than the first current value and greater than the second current value when it is in the forward position thereby to cause the gearbox to shift to a lower gear ratio, said third current value corre- ,sponding to a third speed of the vehicle lower than'said first speed and greater than said second speed.

2. An electrical control device according to claim 1, in which the means for automatically actuating the currentresponsive means between the forward and resetting positions comprises an operating coil connected in theenergizing circuit, and in which said change-over switch is normally closed and operable to an open position for causing the actuation of the current-responsive means at .said third current value, said change-over switch having means to close it after a predetermined period of time after being opened.

3. .An electrical control device according to claim 2, in which said change-over switch is connected in parallel with said coil.

4. An electrical control device according to claim 2, in which said change-over switch is connected in series with said coil. 7

5. An electrical control device according to claim 1, in which said means comprising a change-over switch for causing the current-responsive means to be actuated to the resetting position at a predetermined third current value lower than the first current value and greater than the first current value comprises a capacitor, said changeover switch being connected to connect the capacitor in parallel with said coil when operated to cause the currentresponsive means to be actuated and thereby shunting some of the current flowing in the energizing circuit during charging of the capacitor.

6. An electrical control device according to claim 1, in which said means comprising a change-over switch for causing the current-responsive means to be actuated to the resetting position at the third current value comprises a demagnetizing circuit connected to said current-responsive means, said demagnetizing circuit'including a demagnetizing winding, a normally charged capacitance means, means including the change-over switch for connecting the capacitor across said demagnetizing winding to discharge it into the winding when the change-over switch is operated to cause the current-responsive means to be actuated to the resetting position when it is in the forward position.

References Cited in the file of this patent UNITED STATES PATENTS 1,132,478 Johnson Mar. 16, 1915 2,182,637 Marbury Dec. 5, 1939 2,302,005 Coues Nov. 17, 1942 2,362,570 McLeery Nov. 14, 1944 2,699,507 Schnarz Ian 11, 1955 

